The present invention relates to axles and suspensions.
The basic requirement for an axle is to maintain the road wheels in a predetermined position, or range of positions, relative to the rest of the vehicle. Axles can be of a simple beam design, dating back to at least the Roman chariot and still the most common type of axle today, to complex designs containing dozens of moving parts as may be found on modern luxury cars.
The basic requirement of a suspension is to isolate the driver and passengers from bumps and vibrations, caused by imperfect road surfaces, while also reducing mechanical stresses in the vehicle.
Ever since motorized transport evolved, with higher speeds creating increasing difficulties in the control, comfort and durability of vehicles, there has been constant development in the field of axles and suspensions. This has led to axles and suspensions of increased complexity. Although there have been significant developments in strain energy storage efficiency, such as the coil and parabolic leaf springs, generally speaking the more successful the axle/suspension is in meeting these requirements of control, comfort and durability, the more complex, heavy and voluminous it has become.
To achieve the requirements of an axle/suspension it is necessary to have a flexible component between the wheels and the chassis/frame of the vehicle. This stores the energy transferring from the wheel during a road irregularity and returns it to the wheel a fraction of a second later, the minimum acceleration having been imparted to the chassis/frame.
This invention integrates the energy storage function into the axle itself such that one component functions as both an axle (locating the wheels) and a spring (storing the energy). It does so by using a leaf spring of a unique design. This leaf spring features a cross section that not only varies in cross sectional area, shape and modulus but, in its simplest form, also has a homogeneously formed center section. This complex center section may be formed homogeneously or from several pieces depending on the manufacturing economics of a particular application.
In one aspect of the invention, a vehicle spring-axle apparatus is disclosed for resiliently attaching wheels to a vehicle. The apparatus includes a unitary body having a center portion, first and second center leaves extending oppositely from the center portion, at least one pair of side leaves extending oppositely from the center portion, and means, carried on the ends of the center leaves and the side leaves, for connecting the pair of side leaves and the first and second center leaves to vehicle wheels.
The individual leaves, which connect the wheel hub carriers/knuckles to the frame, may be unequal in length to each other in order to provide wheel camber control, and may be different in cross section or width relative to each other in order to provide different stiffness or spring rate to each other. More then one load/deflection ratio (usually referred to as multiple spring rates) can be derived by differentially pre-tensioning the individual leaf fingers. This is achieved by forming the shape of the leaves in the free condition to be different to the shape of leaves when they are in the installed condition. The different stiffness between the individual leaf fingers gives greater design freedom when providing multiple spring rates. The purpose of multiple spring rates is to provide a soft (low natural frequency) suspension when the vehicle is lightly loaded which becomes stiffer when the vehicle is more fully loaded, without reducing carrying capacity or durability. The spring-axle is capable of providing multiple rates without any additional components to the leaf fingers.
The present spring-axle has one or more of the following features:
1. The spring-axle performs the function of an axle and a suspension using an integral mechanism,
2. The spring-axle uses a minimal number of components to function as a spring-axle,
3. The spring-axle can provide more than one spring rate without additional components,
4. The spring-axle can allow independent movement of wheels mounted to it, positioned on opposite sides of the vehicle, and
5. The spring-axle is adaptable for use on cars, vans, sports utility vehicles, pickup trucks, buses, heavy commercial vehicles, also light or recreational trailers and semi and drawbar commercial trailers.